The 29-year-old Merritt, ranked 180th in the world, clinched victory with a laser shot off the tee at the par-three 16th for a three-foot birdie, and then rolled in a 35-foot birdie putt at the last to cap a 67 for an 18-under-par 266 total.
Merritt, who had missed five consecutive cuts, put himself in position with a course and tournament record 61 in the third round of his 96th career PGA Tour start.
“It's been a long journey the last five, six years,” said Merritt, who credited the transformation in his game to a couple of adjustments he made this week.
“With how good the players are these days it could never have happened, to be quite honest. The level of the people that are out here are tremendous. These guys are the best players in the world and they're only getting better.
“So you have to go out and have a great game plan, pure it all week, make some putts, get some good breaks and luck and maybe have a guy or two stumble at the end.”
Rickie Fowler's long birdie at the 18th for a 69 earned him second place at 15-under, one stroke ahead of Sweden's David Lingmerth (69).
“He went out there and earned it today,” Fowler, who won the Scottish Open three weeks ago, said about Merritt.
“He played some great golf. What he did yesterday (61), to back it up with a solid round of golf, it's what you got to do to win.”
Bill Haas, who tied Merritt for the lead at 17-under after a torrid start capped by a 40-foot birdie putt at the 10th, made four bogeys and a double-bogey the rest of the way for a 70 and a share of fourth place on 12-under.
Kevin Chappell, tied for the overnight lead with Merritt, soared to a 77 and slumped all the way to equal 18th on eight-under, a total he shared with tournament host Tiger Woods, who rebounded from a third-round 74 with a 68. – Reuters
Original source: Merritt wins maiden PGA title